Centrifuge



Feb. 1968 A. c. LAVANCHY ETAL' 3,

CENTRIFUGE 2 Sheets-Sheet 1 Filed Sept. 2, 1966 INVENTORS ANDRE C.LAVANCHY KARL G. REED HARESH M. DESAI YQQZW/QAQM ATTORNEY Feb. 13, 1968A. c, LAVANCHY ETAL v 3,368,747

CENTRIFUGE 2 Sheets-Sheet 2 Filed Sept. 2, 1966 INVENTORS 7 ANDRE c.LAVANCHY KARL G. REED HARESH M}, DESAI United States Patent 3,368,747CENTRIFUGE Andre C. Lavanchy, Devon, Karl G. Reed, Wayne, and

Haresh M. Desai, Bryn Mawr, Pa., assignors to Pennsalt ChemicalsCorporation, Philadelphia, Pa., a corporation of PennsylvaniaContinuation-impart of application Ser. No. 4%,296, Oct. 20, 1965. Thisapplication Sept. 2, 1966, Ser. No. 585,995

Claims. (Cl. 233-7) ABSTRACT OF THE DISCLOSURE In a continuous solidsdischarge centrifuge having a screw conveyor, feed nozzles are providedwhich extend out into the pond and direct the feed towards the solidsdischarge end of the centrifuge bowl.

This application is a continuation-in-part of application Ser. No.498,296, filed Oct. 20, 1965, and now abandoned.

This invention relates to centrifuge feed means. More specifically thisinvention relates to means for delivering centrifuge feed out into thecentrifugebowl in a way which minimizes the disturbance of solidsalready settled in the bowl. It has particular reference to continuouslyoperating solids-discharge centrifuges.

It is old in the art to provide a solidbowl centrifuge with an axialscrew conveyor adapted to move solids toward one end of the bowl fordischarge. Such a centrifuge is shown in the Reed Patent 3,148,145.Conventionally in such centrifuges the feed has been delivered throughanaxial feed tube to a-feed-receiving pocket inside the centrifugeconveyor. From the pocket feed has passed outwardly into the bowlthrough a plurality of nozzles in the conveyor. Such nozzles normallyhave taken the form of a straight tubular element mounted in thecentrifuge conveyor and extending in a radial direction. Usually thefeed nozzles have stopped short of the pond; that is, inward of theliquid level within the centrifuge bowl. In some instances, however, thefeed nozzles have extended out into the pond in an effort-to reduce theturbulence created at the vapor-liquid interface by the incoming feedmaterial.

- Under the present invention its is possible to improve the capacity ofsuch a centrifuge while producing an efliuent of the same clarity. Thisis accomplished by extending thefeed nozzles out into the pondandproviding their distal ends with deflecting surfaces and openingsdirecting the incoming feed toward the solids discharge end of the bowl.Experimentation has indicated that a centrifuge equipped with nozzlesembodying our invention can achieve 1.4 to 1.5 the capacity of theconventionally equipped centrifugewith the same clarity. This is a trulyremarkable and unexpected performance.

Other objects of the invention will be understandable with reference tothe following specification including drawings in which:

FIGURE 1 is an elevational view of a centrifuge having part of the bowlbroken away to show the conveyor inside. The outline of the centrifugeis shown in phantom;

FIGURE 2 is an enlarged fragmentary sectional view on the line 2 2 ofFIGURE 1;

FIGURE 3 is an enlarged fragmentary sectional view taken on the line 33of FIGURE 2;

FIGURE 4 is a fragmentary sectional view of a modified form of feednozzle embodying the invention;

FIGURE 5 is a fragmentary sectional view taken on the line 5-5 of FIGURE4; 7

FIGURE 6 is a fragmentary sectional view of a further modification of anozzle embodying the invention; and

FIGURE 7 is a sectional view taken on line 77 of FIGURE 6.

Briefly; in a continuous solids discharge centrifuge having a screwconveyor the invention is the provision of feed nozzles which extend outinto the pond and 'direct the feed toward the solids discharge end ofthe centrifuge bowl.

, Referring more specifically to the drawings, a centrifuge embodyingthe invention is generally designated 10 in FIGURE 1. It comprises aframe F mounting a bowl 12 having a liquid discharge port 14 at one endand a solids discharge port 16 at the other end. The bowl is providedwith shafts and mounted for rotation to be driven by pulley P.

Within the bowl is disposed an axial screw conveyor 18 which isjournaled in bearings in the end of the bowl and adapted to be rotatedat a speed different from that of the bowl by gear box G to achieve ascrolling action of the solids towards the solids discharge port 16.Speed differential may be regulated by backdrive pulley B. An axiallydisposed feed tube 20.extends inward through a bowl shaft and terminatesinside of the conveyor (FIG. 3). Mounted transversely within the body ofthe conveyor 18 is a diffusion target plate 22 at which the feed isprojected as it issues from the feed tube 20. The target 2211 secured tothe plate directs the feed outwardly and the feed thereby forms ashallow pool within the cup 24 which is also secured to the target plate22. Openings 26 are provided in the cup and aligned openings 28 in thebody of the conveyor. Feed distributing nozzles 30 extend through theseopenings from outside the conveyor. The conveyor is provided with anapertured boss 32 around each opening 28 in the conveyor. The nozzlesare each formed with an annular rib 34 which is received in the openingin the boss. A clamping plate 36 secured the nozzle by its rib 34 in theboss. Suitable sealing means may be provided.

At its distal end the nozzle is provided with a flat baffle 38 whichdeflects the feed in a rightward direction as shown in FIGURE 3. In thatdirection an opening 40 is formed in the tubular nozzle body. In otherwords the feed nozzle opening 40 and the baflie 38 direct the feedtoward the rear surface of the next adjacent conveyor flight 18a. Moregenerally the opening 40 and the baflie 38 direct the incoming feed inthe direction of the end of the centrifuge bowl havingthe solidsdischarge port 16. This is the preferred direction. However, some of thebenefits of the invention may be achieved by directing the opening inthe nozzle and the baffle in a direction opposite the direction ofrotation. Preferably the baflie as shown in FIGURE 3 is angled (angle a)in the range from 45 to 15 from the horizontal.

The opening 40 on the tubular feed nozzle is disposed completely outwardbeyondthe outermost level of the liquid discharge port 14. This providesfor the submerged introduction of feed into the centrifuge pond andminimizes the disturbance caused by the introduction. However, thebaflie is disposed radially inward of the distal edge of the screwflights 18a.

Actual tests using a conveyor equipped with feed nozzles as disclosed inFIGURE 1 and operating on dispersed clay indicated a 1.4 to 1.55improvement in the capacity of a conventional machine having feednozzles as shown in the aforementioned patent for the same clarity ofdischarge eflluent through the port 14.

As shown in FIGURES 4 and 5 a modified form of the invention maycomprise a more open type feed nozzle arrangement. In this arrangementthe conveyor body 18' having the flights 18a is provided with the targetplate 22'. The wall of the conveyor body 18' is provided with an openingwhich is enlarged as at 52 to provide a circumferential surface 54. Inthis version the feed tube takes the form of a scoop-shaped nozzle 56having an enlarged flange 58 which abuts against a shoulder on body 18'and is provided with suitable sealing means 56a in sealing engagementwith the surface 54. Bolt means 60 holds the nozzle on the body. Theinside surface of the scoop-shaped nozzle may be coated with an abrasiveresistance surfacing. In a preferred form the surfacing may be atungsten carbide insert sintered in suitable shape then epoxied into thenozzle opening.

The level of the pond may be at P for instance or P. When the level isat P the bulk of the feed entering through the opening of the nozzle 56is introduced to the pond beneath the surface thereof. When the level ofthe pond is set at P the feed is introduced at the surface level. Ineither case the feed is directed toward the solids discharge end of thecentrifuge toward the rear face of the flight 18a to the right of thenozzle as shown in FIGURE 4.

Within the conveyor accelerator ribs or vanes 64 promote radialacceleration of the feed.

In an actual field test in the plant of a corn processor two identicalscrew centrifuges were set up side by side. In one of the machines thefour feed nozzles were conventional as shown in the US. Patent3,148,145. In the other the nozzles were directional of the type shownin FIGURES 4 and 5, the openings of the nozzles being directed towardthe solids discharge end of the centrifuge. To both machines was led afeed of distillers slops, or stillage, for dewatering. The fine fiberinsoluble solids were present in the feed to a degree indicated in thetable below and the feed rate for each machine ranged between 25 to 40gallons per minute. A series of readings were taken, readings on bothmachines for each of a number of feed input rates. In the table belowthe electrical load on the machine fairly represents the feed rate sinceboth machines had identical no load readings. The results provide adirect comparison between operation with the conventional nozzles andthe directional nozzles.

Insoluble solids in discharges, percent wJw. Insoluble Amperage From theabove table it can be seen that there was a marked reduction in thesolids content of the efiluent. The solids content of the effluent ofthe machine having the conventional nozzles varied in the range fromroughly 4 to 16 times the solid content of the effluent of thedirectional nozzle machine for the same feed.

With the same set-up, the two machines being in sideby-side comparison,a series of readings were then taken on a feed comprising a slurry offine fibers from wet corn milling. The feed was in the range of 25 to 50gallons per minute. The results may be tabulated:

Insoluble solids in discharges, percent w.lw.

Insoluble Amperage Data not available.

From the above it can be seen generally that in using directionalnozzles the liquid efliuent contained in each case is roughly a tenth ofthe insoluble solids of the screw centrifuge having conventionalnozzles.

Other direct comparisons were made of the same type machine, one havingconventional nozzles and the other directional nozzles of the type shownin FIGURES 4 and 5. For instance, the soft flocky non-packing solids inunderflow from a settling basin containing activated domestic sewagewere centrifugally dewatered in the two machines. With the directionalnozzle machine as shown in FIGURES 4 and 5 a reasonable settling in thebowl could be achieved employing an economical level of polyelectrolytecoagulant. Using the screw machine with the conventional feed nozzles,on the other hand, the amount of polyelectrolyte necessary to effect areasonable separation was economically prohibitive. The advantage of thedirectional nozzlesis abundantly clear.

A modified feed nozzle is shown in FIGURES 6 and 7. The conveyor body18" formed with the flight 18a is provided with an opening 70communicating with the feed supply on the inside of the conveyor. Theopening is reinforced with a collar 72 to which is secured by bolt means74 a clamping ring 76. The clamping ring is undercut as shown to holdtightly the flange 78 of the nozzle proper 80. The opening through thenozzle 80 terminates upwardly as shown in FIGURES 6 and 7 in a fiatmouth 82 directed toward the solids discharge end of the centrifuge. Themouth is connected to the body of the nozzle 80 by a transition element84.

In the preparation of this application the following art was considered:US. 3,148,145, 2,600,372, 775,320, and 750,668.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or central attributes thereof and,accordingly, reference should be made to the appended claims rather thanthe foregoing specification as indicating the scope of the invention.

We claim:

1. In a centrifuge comprising a hollow bowl having a solids dischargeport at one end and a liquid discharge port at the other end and outwardfrom the solids discharge port, a conveyor having screw flights andmounted on the axis of the bowl for moving solids toward the solidsdischarge port, means for rotating the bowl and the conveyor atdifferent speeds, and feed means including a feed pipe extending axiallyinto the conveyor, the conveyor having a feed receiving pocket and atleast one feed nozzle extending outward from the conveyor into the bowl,the distal end of the feed nozzle having an opening facing toward thesolids discharge port and adapted to direct feed mixture in thatdirection and toward the rear surface of the adjacent screw flight,there being clear space between the latter and said opening.

2. A centrifuge as described in claim 1 wherein the feed nozzle extendsto a point located at a greater radius than the liquid discharge portand having an opening to deliver feed to the bowl at a level radiallyoutward from the liquid discharge port.

3. A centrifuge as described in claim 2 wherein the distal end of thefeed nozzle is disposed inward of the distal edges of the screw flights.

4. A centrifuge as described in claim 1 wherein the inside of the nozzleis coated with a hard surfacing material.

5. A centrifuge as described in claim 1 wherein the feed nozzle has anenlarged portion of its base which abuts against an outwardly facingshoulder about an opening in the conveyor and a clamping plate holds theportion inward against the shoulder.

References Cited UNITED STATES PATENTS Van Kirk 2337 Milliken et a1.2337 Millard 233-47 Lyons 2337 Fitzsimmons 23347 Reed 2337 Moore 51-11HENRY T. KLINKSIEK, Primary Examiner.

